How to stop Redirect (forms authentication) from 'root' URL?
Solution 1:
The location tags can target specific files and subfolders but can't target the root (i.e. /). One option is to start with all allowed and block files and folders. The problem there is that if you forget to do this for new folders your site can be vulnerable.
I believe that you can use URL Rewrite to handle the default doc and point to default.aspx with a 'rewrite' rule. For example, in the url match, use "^$" which means exactly nothing. Then for the action, rewrite to /default.aspx. Then .NET will see /default.aspx and won't redirect for you.